Flow barrel polishing is a method for inputting a mass configured by a workpiece that is a polishing target and a media that is a polishing material into a polishing bath, and for polishing the workpiece while causing the mass to centrifugally flow using a rotary disc provided on a bottom of the polishing bath. One example of the method is disclosed in Japanese Patent Application Laid-Open No. 8-11057 (Japanese Patent Number 3343701). As shown in FIG. 1, according to this flow barrel polishing method, the workpiece and the media are rubbed against each other to polish the workpiece surface while the mass is caused to flow in a toroidal fashion by a combination of a horizontally rotatable flow running along a rotation direction of the rotary disc and a vertically rotatable flow rising along an inner wall surface of the polishing bath and running downward in a central direction when reaching an uppermost portion by a centrifugal force.
The conventional flow barrel polishing has, however, disadvantages in that the media is gradually worn as the polishing progresses, a mass amount is reduced, a frictional force between the workpiece and the media is reduced, and a deterioration in a polishing capability is thereby unavoidable. These disadvantages are conspicuous particularly in dry flow barrel polishing.